1. Field of the Invention
The invention relates to a binocular optical instrument equipped with image vibration correction function.
2. Description of the Related Art
Japanese Laid-Open No. Hei-2-284113 proposed a binocular capable of correcting image vibrations caused by shaking hands during observation. The correction in said invention is accomplished in a prism binocular shown in FIG. 9 of the present application by rotating all or a part of an erecting optical system consisting of a pair of prisms P and group of mirrors M in the yaw and pitch directions relative to the fixed part of the binocular so as to suppress the displacements of the focused image formed by the objective optical system in the yaw and pitch directions.
Japanese Laid-Open No. Hei-7-84223 proposed as shown in FIG. 10 of the present application a system wherein a variable apical angle prism (“VAP”) on the side of the object relative to the focal plane of the object optical system contained in the left and right lens barrels 91L and 91R, so that the vibrations of the image can be corrected by suppressing the displacements of the focal image formed by the object optical system in the yaw and pitch directions by changing the reflective and refractive angles of this variable apical angle prism in the yaw and pitch directions.
However, the binocular proposed by Japanese Laid-Open No. Hei-2-284113 has a problem in that it requires an elusive use prism P for adjusting the eyepiece width (spacing between eyepieces), which makes it difficult to present a compact binocular, since a part of the mirror group M is shared by both the left and right sides to correct the vibrations despite the fact that it provides an advantage in that a pair of light beams that have passed through a pair of object optical systems can be simultaneously correction controlled for vibrations.
Also, the above binocular comprises an erecting optical system such as an erecting prism so that it is not applicable to a binocular that does not have an erecting optical system, for example, a Galilean binocular. More over it requires the use of high precision components in order to keep the difference of the left and right optical axes within a certain limit, so that it is difficult to make construction inexpensive.
On the other hand, the binocular proposed by Japanese Laid-Open No. Hei-7-84223 requires an additional optical part (VAP) to be used in order to suppress the displacement of the focal image by bending the optical axis, which causes restrictions in terms of reducing cost and size, in addition to a problem in that it requires a careful optical axis adjustment between the left and right sides as the left and right lens barrels are connected so as to be able to rotate relative to each other by means of a connecting pin RP, which makes the system more cumbersome to deal with.